i totally agree with the perfume factor. my friends son used to cry like crazy whenever grandma tried to hold him. Only ONE grandma. Her perfume was soo strong! It was my friend's MIL, so she had a difficult time telling the grandma that her son is not taking to her because of the strong "odor".
I think you have a very nice nanny. I'm sure you know very well. i really respect your compassion for people and their circumstances. I would consider the same things. Hate it when some people just have the "natural' reaction to just "attack", "fire", "judge", "sue" for every little thing. There's no faith in humanity anymore. Not everyone's lives are so simple. People's circumstances are diferent. Not everything can be resolved with one formula. I'm a stay at home mom and I consider it a total blessing. But I'm one of the the lucky ones.
Anyway, this nanny is very lucky to be working for you. So hopefully her not wearing any perfume will be the answer.
Let us know what happens.